1. Field of the Invention
This invention relates to a process for preparing refractory borides and carbides. The process is operative at temperatures considerably lower than those in general use for the preparation of such refractory materials.
As is well known, certain borides and carbides are highly refractory and are useful in the fabrication of products capable of withstanding high temperatures and physical and chemical attack. Titanium diboride (TiB.sub.2), for example, is useful in the fabrication of bushing materials, bearing liners, nozzles and wear plates. Its electrical conductivity makes it useful as a cathode material in the electrolytic reduction of aluminum ore. Silicon carbide (SiC), for example, exhibits high thermal conductivity and low thermal expansion, making it particularly resistant to thermal shock. It is extensively used in a wide variety of applications.
2. Discussion of the Prior Art
As described in U.S. Pat. No. 3,004,830, borides are generally manufactured by heating an oxide of the metal whose boride is to be prepared and boric oxide or boric acid together with a carbon source at a high temperature in an electric arc furnace. U.S. Pat. No. 4,405,021 describes the preparation of titanium diboride by the heterogeneous reaction of gaseous boron trichloride with titanium trichloride or titanium dichloride at 600.degree.-750.degree. C. and 600.degree.-1100.degree.C., respectively.
Carbides are generally manufactured by heating silicon dioxide or the metal whose carbide is to be prepared, usually as its oxide or chloride, with a carbon source, such as coke or anthracite coal, at temperatures usually not less than 1400.degree. C., and generally approaching 2000.degree. C. or even higher.